The aggregation rate of red blood cells (RBC) is known to increase in certain pathological conditions, and the aggregated cells presumably influence the microcirculation in the tissues of the body organs. To quantify the RBC aggregation rate, many techniques have been developed. Measurement of erythrocyte sedimentation rate (ESR) by Fahraeus was the first and is disclosed in a paper by him in 1921 entitled "Suspension-Stability of the Blood" in Acta Med. Scand. 55:1-228. However, it remains doubtful whether the ESR represents a suitable measure for this purpose.
Viscometry of whole blood at very low shear rates was the next technique and is disclosed in the following papers: Benis A. M., and J. Lacoste, 1968, "Study of erythrocyte aggregation by blood viscometry at low shear rates." Circ. Res. 22:29-41; Wells, R. E., Jr., T. H .Gawronski, P. M. Cox, and R. D. Perera, 1964, "Influence of fibrinogen on flow properties of erythrocyte suspensions." Amer. J. physiol. 207:1035-1040; and Chien, S., S. Usami, H. M. Taylor, J. L. Lundberg, and M. I. Gregersen, 1966, "Effect of hematocrit and plasma proteins on human blood rheology at low rates of shear." J. Appl. Physiol. 21:81-87. But this technique was criticized in a paper by H. Schmid-Schonbein, G. Gallasch, E. Volger, and H. J. Klose entitled "Microrheology and protein chemistry of pathological red cell aggregation (blood sludge) studied in vitro" in Biorheology, 1973, Volume 10, pages 213-227. They argued that the hydrodynamic effects of pathological RBC aggregates on the torque transmission through RBC suspensions constituted an insufficient system for rheological quantification of the RBC aggregation, and that the enhanced tendency to aggregation also prevented accurate measurement of the viscous effect in flow due to pronounced phase separation.
Quantitative evaluation of the rate of RBC aggregation (rouleaux formation) was successfully performed by Brinkman et al by measuring the light reflection ("syllectometry") of the blood--see a paper by Brinkman, R., W. G. Zijlstra, and N. J. Jansonius in 1963 entitled "Quantitative evaluation of the rate of rouleaux formation of erythrocytes by measuring light reflection ("syllectometry")" in Proc. Kon. Ned. Akad. Wet., Ser. C (Biol. Med.) 66:236-248. Subsequently, the principle of photometric aggregometry has been extended by several investigators as disclosed in the following papers: Berman, H. J., and R. I. Fuhro, 1973, "Quantitative red blood cell aggregometry of human and hamster bloods." Proc. VIIth Conference on Microcirculation (Aberdeen 1972) Karger, Basel, 117-125; Usami, S., and S. Chien, 1973, "Optical reflectometry of red blood cell aggregation under shear flow." Proc. VIIth Conf. on Micro-circulation (Aberdeen 1972) Karger, Basel, 91-98; Scmid-Schonbein, H., J. V. Gosen, L. Heinich, H. J. Klose, and E. Volger entitled "A counter-rotating "rheoscope chamber" for the study of the microrheology of blood cell aggregation by microscopic observation and microphotometry", 1973, Microvascular Research 6:366-376; and Shiga, T., K. Imaizumi, N. Harada, and M. Sekiya, 1983, "Kinectics of rouleaux formation using TV image analyzer." I Human erythrocytes, Amer. J. Physiol. 245:H252-H258. However, these techniques are rather complicated for common use.
Recently Schmid-Schonbein et al constructed an automatic red cell aggregometer, improving their "rheoscope", which permits transmission photometry of RBC aggregate formation after shearing the blood in a counter-rotating cone chamber - see a paper by Schmid-Schonbein, H., E. Volger, P. Teitel, H. Kiesewetter, U. Dauer, and L. Heilmann entitled "New hemorheological techniques for the routine laboratory" in RACD Vol. II Supplement 1981. However, such aggregometer is expensive and has problems in that asymptotical baseline is unstable.